1. Field of the Invention
This invention relates generally to pipe accessories and more particularly to a tapping sleeve that allows an existing pipe to be tapped and provides a sealed outlet for attaching a branch line.
2. Description of Related Art
Water, gas, and other fluid pipelines are used to deliver fluids from one location to another. Many times these pipelines are buried, but they may also be located above ground. The pressure of the fluid within the pipe will vary depending on the type of fluid and the size of the pipe, but it is possible to have relatively high pressures. It is a very common need to expand pipelines by adding branch lines to divert fluids carried by the pipeline to new locations. Similarly, if an existing branch becomes corroded, it may be necessary to replace the branch by tapping into the pipeline at a new location.
Tapping sleeves are devices that allow in-service tapping of a pipeline. A tapping sleeve is installed around a pipe, a branch line is attached to the tapping sleeve, and a hole is tapped in the pipe. By using a tapping sleeve, the branch line can be attached without having to de-pressurize and clear the pipeline. The tapping sleeve typically includes a pair of sleeve members and a sealing device that are attachable around the pipe.
Tapping sleeves are manufactured in many different shapes and sizes. Some existing tapping sleeves use gaskets or o-rings to locally seal around the hole that is being tapped in the pipeline. While these sealing rings may work fine in pristine laboratory conditions, they are more difficult to properly install under the often rugged conditions experienced by persons working on a pipeline. Sometimes the pipes to be tapped are located underground, and dirt and other contaminants could interfere with the proper sealing of these devices. Typically o-rings and gaskets installed locally around the tapped hole have relatively small surface areas that actually contact the pipe. These small surface areas decrease the likelihood of an effective seal when dirt and other contaminants are introduced. Another problem with these gaskets is that they fail to electrically insulate the sleeve members from the pipe, which may be a requirement when tapping pipelines carrying certain fluids.
Other existing tapping sleeves use larger, “full circle” gaskets that cover the entire outer surface of the pipe underneath the sleeve members. These gaskets are typically split into two sections. One section of the gasket is glued to the inner wall of a first sleeve member, while another section is glued to the inner wall of a second sleeve member. The gasket on one of the sleeve members usually includes one or more small pieces of armor that bridge the gap between the two sleeve members as the sleeve members are attached around the pipe. The gaskets are glued to the sleeve members to prevent “flow” of the gasket. If the gaskets were not glued, the gasket could potentially slide out of the end of the sleeve members, which would cause a loss of bolt torque on the tapping sleeve, and would likely breach the seal surrounding the tapped hole. One problem with glueing full-circle gaskets to the sleeve members of the tapping sleeve is that the gasket cannot be easily interchanged. It may be desirable to use a different size gasket for different pipe sizes while using the same sleeve members. It may also be desirable to use a gasket made of a different material depending on the type of fluid being carried by the pipe.
A need therefore exits for an improved tapping sleeve having a gasket that fully insulates the sleeve members of the tapping sleeve from the pipe. A need further exists for a gasket that is easily replaceable or interchangeable with the sleeve members and is not bonded to the sleeve members. Since the gasket should not be permanently bonded to the sleeve members, a need exists for controlling the flow of the gasket material as the sleeve members are tightened around the gasket and the gasket is compressed. More specifically, a need exists for preventing the gasket material from blocking the tapped hole in the pipe.